The invention relates to apparatus for forming and controlling air currents, especially air currents issuing from an air-permeable perforate surface.
In buildings and in plants of widely varying kinds and used for a wide variety of purposes, for example in plants for the spray-painting of the bodywork of cars, it is known to supply fresh air to an enclosed space through a perforated surface, preferably through the ceiling of a room. For this purpose there is generally provided a cavity, positioned behind or above the perforated surface, to which a fan or blower is connected. The fresh air so supplied issues from the perforated surface opposite the cavity in a relatively uniform array of numerous low-velocity air currents which may, for example, carry particles of dyestuff, paint, gases, solvents or other contaminating or air-polluting matter through the room, to leave it through outlets which are usually provided in the room surface opposite the perforated surface, e.g. in the floor.
Ventilating systems of this kind are, on the whole, quite useful; they have, however various serious disadvantages. For example, systems of this kind are generally incapable of allowing for the fact that the optimum quantity and optimum velocity of the ventilating air are different in various parts of a room. Instead, the entire system is adjusted to supply the requirements of the particular area of the room most in need of ventilation. However, the ventilating air supplied in cold and moderate climatic regions is generally heated, and considerable losses of energy thus result from the fact that the maximum quantity of heated ventilating air also circulates through areas of the room which are less in need of ventilation. In addition, problems may arise from drafts obtaining in certain zones of the room.
These disadvantages have not remained unnoticed. Thus, for example, it is proposed in French Pat. Specification No. 2,107,262 to improve the air circulation by dividing a ceiling into various sections of ventilation, each section serving a different purpose. In accordance with that French patent specification, a central section of the ceiling is provided with uniformly spaced perforations ensuring uniform circulation through a central section of a room, the central section of the ceiling being surrounded by channels which, through continuous gaps, produce so-called "air curtains" for the purpose of screening the central section of the room.
Such an arrangement is not only highly specialized, in that it is intended for use only in very special cases, but it is also very expensive since it requires the provision of separate air inlets for each individual other section of the ceiling. An exact adjustment of the air-curtain flow in various areas of the ceiling is very difficult, even impracticable, since a considerable pressure drop has to be expected owing to the lengths of the individual channels or ducts. For these and other reasons, such known system cannot be considered to be suitable to solve the afore-mentioned problems, except in a few special cases.
Copending application Ser. No. 615,971 of George Walker, filed Sept. 19, 1975, now U.S. Pat No. 4,048,912 and entitled "Colour Spray Booth and Method for Ventilating the Same" describes an air ventilating system in which ventilating air currents are caused to flow downward through a perforated ceiling to exit through openings in a floor, while at the same time separate air ducts supply air under pressure to one or more arrays of nozzles or the like which provide air curtains for separating the room into differently-ventilated areas. While suitable for many purposes, this system is again somewhat expensive, and once installed, rather difficult to rearrange to accommodate changes in desired operating characteristics.
It is therefore an object of the invention to provide a simple and inexpensive apparatus for forming and controlling air currents issuing from a perforate surface into a region in which changed requirements can be quickly and fully met and the invention applied in widely varying fields and to various extents by virtue of its high flexibility of construction and adjustability.